The antioxidant action of synthetic oestrogens involves decreased membrane fluidity: relevance to their potential use as anticancer and cardioprotective agents compared to tamoxifen?

The synthetic oestrogens diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol are known to be good antioxidants, and we now report that they decrease membrane fluidity, in ox-brain phospholipid liposomes. The order of effectiveness was diethylstilboestrol > hexoestrol > 17 alpha-ethynyloestradiol and a good positive correlation was demonstrated between decreased membrane fluidity and antioxidant ability (measured as inhibition of liposomal lipid peroxidation: correlation coefficient, r = 0.99). This ability of diethylstilboestrol, hexoestrol and 17 alpha-ethynyloestradiol to decrease membrane fluidity is suggested, therefore, to be the mechanism of their antioxidant action. The membrane-modulating antioxidant action of these synthetic oestrogens is compared to that of tamoxifen and their potential use as anticancer and cardioprotective agents is discussed.